In general, a projection type image display apparatus such as a liquid crystal projector is provided with three sheets of liquid crystal panels corresponding to a red light, a green light, and a blue light obtained by splitting the light from a light source lamp, and optical parts such as polarizing plates disposed at the incident side and the outgoing side of each liquid crystal panel, and a polarizing beam splitter (PBS) aligning the polarized direction of the light from the light source lamp.
As a light source lamp, a high-pressure mercury lamp, a metal halide lamp, and the like which emit high intensity light in high temperature are used, and the liquid crystal panel processing a high-intensity light and the optical parts such as the polarizing plates and the PBS also increase in temperature. When the liquid crystal panels and the optical parts such as the polarizing plates and PBS increase in temperature, their performance and life span are reduced, and therefore, they need to be cooled.
Japanese Patent Application Laid-Open Publication No. 2001-083637 discloses a cooling mechanism that cools three sheets of liquid crystal panels corresponding to a red light, a green light, and a blue light, respectively, and the polarizing plates disposed at an incident side and an outgoing side of each liquid crystal panel by one set of the fan every color, that is, a total of 3 sets of the fans.
Meantime, since three sheets of the liquid crystal panels corresponding to the red light, the green light, and the blue light, and the polarizing plates disposed at the incident side and the outgoing side of each liquid crystal panel and the like are different in temperature rise and in degree of ultraviolet degradation every color, a required cooling amount is also different. Particularly, since the blue light is close to an ultraviolet region, to avoid the ultraviolet degradation, a required cooling amount becomes large.
The projection type image display apparatus such as a liquid crystal projector and the like has come to require the enhancement of luminance by the raised output of the light source lamp, the miniaturization of the apparatus, and a reduced cost (miniaturization of the liquid crystal panel and the like) all together, and hence, the amount of light per unit area of high luminance has been on the increase.
However, the conventional art which performs cooling by one set of the fan every color has been unable to cope with the model whose amount of light per unit of high luminance has increased. As the countermeasure, when the output of the fan (the number of rotations) is increased, the noise of the fan is increased. Further, there has been a problem that the cooling of the PBS needs to be also performed.